Programme for Research-Development-Innovation on Space Technology and Advanced Research – STAR
(Romanian Space Agency)

Results

  • High quality YBCO thin films with a strong orientation on c axis have been obtained with Pulsed Laser Deposition  PLD technique by INFLPR team using the temperature  control equipment  acquired during  this project.  The thin films quality has been strongly improved with post deposition 450 degrees annealing treatment in oxygen athmosphere. The films obtained with RF assisted PLD are a axis oriented.

    Deposition and characterization of YBCO thin film

AFM image of YBCO
thin film on STO
substrate.

Difractogram of YBCO
thin layer deposited with
PDL on STO substrate.

  • The YBCO sensitive layers have been electrically tested at IMT-Bucharest  with the available cryogenic equipment. The transition from superconductor state to the normal conduction state have been observed to appear between 80 and 90 K. A preliminary test  has shown the increase of the resistivity at irradiation with an IR source. The strong response has been obtained in the middle of the transition region.

    Characterization of YBCO thin film electrical properties

Variation of resistivity with
temperature

Relative variation of the resistivity at infrared irradiation
  • A versatile read-out circuit  for the bolometers have been designed and fabricated. This read-out circuit allows both voltage or curent polarization and can be adapted for the four-point measurement which is the most appropriate read-out method  for superconductors materials.  The proposed read-out system can be easily controlled by user.

    design of the read-out circuits

Scheme of the read-out circuit

 

  • The increasing of the radiation absorption have been studied both from theoretical and experimental point of view.  The thin layer of silver deposed with ink jet printing technique presented a very good absorption spectra  over midlle and long infrared range.  Another method for increasing the absorption levels is based on the configuration of thin metallic layer. The FDTD analysis demonstrated  a significant improvement  of the absorption over some region of the IR spectrum if metamaterials  based on metallic split rings are considered.


    Absorption spectrum of thin silver layer deposited with ink-jet printing technique

    Model of split-ring resonator for enhancing the radiation absorption

    The absorption of the sensitive configuration. YBCO layer – black line; YBCO/SiN  configuration  -red line ; YBCO/SiN +SRR;configuration – green line YBCO/SiN +SRR  iincluded in SiN - blue line.